(1) Field of the Invention
This invention relates to a flywheel suitable for use in a tape recorder or the like.
(2) Description of the Prior Art
Flywheels employed in tape recorders and the like are generally of such a type that a shaft extends centrally through a metallic rotary body formed as an integral member by a die or the like and is fixed to the body. They however require many production steps especially where pulleys are formed in the metal disks, resulting in higher production costs.
With the foregoing in view, it has recently been contemplated to produce flywheels of the above sort by combining annular metal plates and pulleys made of a synthetic resin (see, for example, Japanese Utility Model Laid-Open No. 112752/1983 or U.S. patent application Ser. No. 06/726,297 filed on Jan. 27, 1983 now abandoned. One example of such recent flywheels will next be described in brief with reference to FIGS. 7 and 8, which are cross-sectional side view and top plan view of the exemplary flywheel respectively.
In FIGS. 7 and 8, numeral 71 indicates an annular metal plate while numeral 72 designates a pulley made of a synthetic resin (may hereinafter be called "plastic pulley" for the sake of brevity). They are coaxially superposed and fixed to each other. A shaft, for example, a capstan 73 is centrally and fixedly inserted through the pulley 72. As exemplary means for fixing the annular metal plate 71 and plastic pulley 72 to each other, the plastic pulley 72 is provided with four hooks 74 which are maintained in engagement with an inner peripheral edge portion of the annular metal plate 71. Since the unification of the annular metal plate 71 and pulley 72 cannot be achieved fully by the interlocking hooks 74 alone, a double-tack sheet 75 is also interposed therebetween to adhere them firmly with each other.
Flywheels of the above-described sort are however accompanied inter alia by the following problems. It is necessary to apply the double-tack sheet 75 to either one of the annular metal plate 71 and plastic pulley 72 before superposing them with each other. This step is very cumbersome. If the double-tack sheet 75 should be omitted, problems will arise if the hooks 74 undergo plastic deformation during a high-temperature test which is conducted as the final step of the production process of the flywheel. Namely, the hooks 74 will lose their holding function for the annular metal plate 71, leading to such problems that the annular metal plate 71 and plastic pulley 72 may be separated from each other and/or may be caused to idle relative to each other.